Get current day count from current month except holidays - sql

Question

I am a beginner in SQL. I have to fetch current day count(Day Number) from current system month, which should not consider the weekend (Saturday and Sunday).
For example if I am executing the query today (05-Dec-2018) then my output should be 3 (current date is 05-12-2018, here 1st Dec is Saturday and 2nd dec is Sunday. I don't want to include the weekends in this calculation. So Monday (3rd Dec) will be 1, Tue (4th Dec) will be 2 and Wed (5 Dec) will be 3.
Any help for this highly appreciated.

Answer 1

You do not need to use a hierarchical query and can do it independent of the NLS settings using TRUNC( date_value, 'IW' ) to find the start of the ISO week, which is always a Monday.
So:
TRUNC( SYSDATE, 'IW' ) - TRUNC( TRUNC( SYSDATE, 'MM' ), 'IW' )
Will find the number of days between the start of the ISO week containing the first day of the month and the start of the current ISO week. Multiplying this by 5/7 will give the number of week days.
Then all you need to find is how many of those days occurred in the previous month and subtract them. This can be found using:
LEAST( TRUNC( SYSDATE, 'MM' ) - TRUNC( TRUNC( SYSDATE, 'MM' ), 'IW' ), 5 )
and how many days need to be added on for the current week; which is given by:
LEAST( TRUNC( SYSDATE ) - TRUNC( SYSDATE, 'IW' ) + 1, 5 )
So the total can be found using:
SELECT ( TRUNC( SYSDATE, 'IW' ) - TRUNC( TRUNC( SYSDATE, 'MM' ), 'IW' ) ) * 5 / 7
+ LEAST( TRUNC( SYSDATE ) - TRUNC( SYSDATE, 'IW' ) + 1, 5 )
- LEAST( TRUNC( SYSDATE, 'MM' ) - TRUNC( TRUNC( SYSDATE, 'MM' ), 'IW' ), 5 )
AS Num_Week_Days
FROM DUAL;
An example with multiple days:
WITH calendar ( date_value ) AS (
SELECT DATE '2018-12-01' + LEVEL - 1
FROM DUAL
CONNECT BY LEVEL <= 15
)
SELECT date_value,
TO_CHAR( date_value, 'DY' ) AS day,
( TRUNC( date_value, 'IW' ) - TRUNC( TRUNC( date_value, 'MM' ), 'IW' ) ) * 5 / 7
+ LEAST( TRUNC( date_value ) - TRUNC( date_value, 'IW' ) + 1, 5 )
- LEAST( TRUNC( date_value, 'MM' ) - TRUNC( TRUNC( date_value, 'MM' ), 'IW' ), 5 )
AS Num_Week_Days
FROM Calendar;
Output:
DATE_VALUE DAY NUM_WEEK_DAYS
---------- --- -------------
2018-12-01 SAT 0
2018-12-02 SUN 0
2018-12-03 MON 1
2018-12-04 TUE 2
2018-12-05 WED 3
2018-12-06 THU 4
2018-12-07 FRI 5
2018-12-08 SAT 5
2018-12-09 SUN 5
2018-12-10 MON 6
2018-12-11 TUE 7
2018-12-12 WED 8
2018-12-13 THU 9
2018-12-14 FRI 10
2018-12-15 SAT 10

Answer 2

This type of query is really easy to write if you maintain a calendar table in your database. Here is a query that generates a partial calendar of all days from the start of the month up to and including today. Then we can count the number of weekdays.
select count(*)
from (select trunc(sysdate, 'MM') - 1 + level as d
from dual
connect by level <= trunc(sysdate, 'DD') + 1 -- Today
- trunc(sysdate, 'MM') -- First day of current month
)
-- Exclude weekends
where to_char(d, 'DY', 'nls_date_language=american') not in('SAT', 'SUN')
;

Answer 3

You might use this sql select statement with connect by level clause :
select sum(dy) "Total Day"
from
(
select (case when to_char(sysdate-level+1,'D','nls_date_language=turkish') in (6,7)
then 0
else 1 end ) as dy
from dual
connect by level <= to_number(to_char(sysdate,'DD'))
);
Total Day
---------
3
You can try the other cases by replacing both sysdate keywords with sysdate + 3, sysdate + 4 , sysdate + 5 ... etc.

Answer 4

This should work for SQL Server
SET #today= '2018-12-14'
SET #firstDate = (SELECT DATEADD(month, DATEDIFF(month, 0, #today), 0) AS StartOfMonth);
WITH allDates AS
(
SELECT
#firstDate AS DT
UNION ALL
SELECT
DATEADD(dd, 1, DT)
FROM
allDates as S
WHERE
DATEADD(dd, 1, DT) <= #today
)
SELECT count(*) FROM allDates where DATENAME(dw,DT) <> 'Saturday' and DATENAME(dw,DT) <> 'Sunday' option (maxrecursion 0)